Fortunately the msconfig utility is still included in Vista while other tools are no longer seen. The article at the link here covers editing the boot.ini for XP but also shows how to change the boot order with the boot.ini section in the msconfig utility. Likewise Vista has it's own section when you open it there instead of always going into the bios unless you had unplugged one drive when installing Windows on the other and that entry is not seen as an option to load.
When Vista first loads you should see the option for "previous version of Windows" there. That will bring you to a second screen showing the xhoice for loading XP if included in the Vista mbr. The EasyBCD has one button for simply selecting the default OS there as well called the configure boot. A second one is the manage boot loader. Once you open that you simply select the version of Windows or OS you want to see auto load and set it there. For a look at the XP msconfig boot.ini section go to
How to Use and Edit Boot.ini in Windows XP Vista will have a boot loader section that looks the same.